António Lopes

The influence of the summer sea breeze on thermal comfort in Funchal (Madeira). A contribution to tourism and urban planning.

To urism plays a crucial role for the development of coastal areas. Despite the mildness of Madeira’s climate, very hot days can occur during summer, a situation to which most tourists from northern Europe (the majority of foreign tourists) are poorly adapted. As sea breezes strongly contribute to moderate heat stress in urban environments, their influence on the thermal comfort on the island has been studied. Sea breezes occurred on 84 % of the days during the period under study (May to October 2006). They usually start around 09:30 h and end after 22:00 h, with an average duration of about 12:50 hours and a mean velocity of 2.9 m/s. Physiologically Equivalent Temperature (PET) was used to evaluate the thermal comfort of a sample of days during the summer of 2006. It was concluded that most of the sites in the city are “slightly comfortable” during normal days with sea breeze, but only shore sites and the highest green areas offer some comfort during hot days. Inside the city, the thermal perception is generally “hot” and strong heat stress can occur. As sea breezes are important to mitigate heat stress, some basic guidelines were presented: urban planners should take advantage of this wind system avoiding dense construction near the shoreline that would act as a barrier to the renewal of the air inside the city. In terms of tourism, planners and local authorities should provide solutions to mitigate the negative effects during hot periods, creating a system to warn and relocate more vulnerable tourists to places near the shore line, to the mountains, to gardens and air-conditioned buildings. In combination with other components (beauty of the island, gastronomy, cultural values and safety), climate information can be a factor of attractiveness to tourists. Zusammenfassung

Wind Risk Assessment in Urban Environments: The Case of Falling Trees During Windstorm Events in Lisbon

Planting trees brings many benefits to the urban environment (Fabiao 1996; Jim and Liu 1997; Nilsson et al. 2000; Saebe et al. 2003; Soares and Castel-Branco 2007). Trees have a moderating effect on the urban microclimate and improve the physical, biological and chemical aspects of the urban environment, namely by reducing the urban ‘heat island’ effect (Alcoforado 1992), by acting as a barrier against strong wind channelling (Lopes 2003), by protecting urban surfaces from direct sunlight (McPherson and Muchnick 2005), by capturing air pollutants and dust in urban areas (Freer-Smith et al. 2004) and by increasing the biodiversity, providing habitat for birds and small mammals (Clergeau 1996).

Lisbon Urban Heat Island Updated: New Highlights about the Relationships between Thermal Patterns and Wind Regimes

Urban growth implies significant modifications in the urban climate. To understand the influence of the city of Lisbon on the urban boundary layer, a mesoscale meteorological network was installed in 2004. The main goals of the present study are to update the results of the research published in 2007 and to bring more precise information about the relationship between the Urban Heat Island (UHI) and the regional and local wind systems. The highest frequencies of the UHI were found in the city centre (Restauradores). In the green park of Monsanto, the highest frequency occurred between −2 and 0°C. During the summer, the effect of the breezes was observed in Belem, lowering the temperature. The “strong” UHI (intensity >4°C) occurred more often during the summer, with median values of 2°C by night and 1.8°C by day. The highest frequencies of UHI occurred for winds between 2 and 6u2009m/s and were not associated with atmospheric calm, as pointed out in the literature. Winds above 8u2009m/s inhibit the occurrence of strong UHI in Lisbon. Summer nighttime strong UHI should be further investigated, due to the heat stress consequences on the population and probable increase of energy consumption.

An integrated approach for wind fields assessment in coastal areas, based on bioindicators, CFD modeling, and observations

Wind-deformed trees can be good bioindicators of the mean wind speed and prevailing wind directions. The current research used bioindicators, computational fluid dynamics (CFD), and linear models to assess the wind fields in the windy coastal area of Cascais/Portugal. The main objectives of this research are to assess mean speed and directions of winds by using bioindicators and modeling techniques and to correlate both results in order to assess the best methods. The results obtained with the bioindicators showed that carpeting, the most severe deformation, was observed near the shoreline showing that the highest wind speeds are felt in this sector. Inland, where the winds have lower mean speeds, flagging forms are more frequent. When correlated with the bioindicators, the linear model gave better results than CFD models. We can conclude that in areas with good wind potential, the use of bioindicators can be a good alternative in the absence of wind data.

An Assessment of Falling Trees Due Strong Winds in Lisbon: Affected Species and Microclimatic Simulation

Fallen trees due to strong winds are well recorded in Lisbon. However, specie 13 identification is needed to increase urban trees management. This paper aimed the identification of 14 the most vulnerable trees to strong winds in Lisbon, through a hybrid approach method by 15 proximity. The occurrence database was compiled together with basic structural city maps. Four 16 criteria were designed to presuppose the trees specie names by approximation: i) Trees must be 17 within 15 m from the street center; ii) At least 3 individuals within 30 m from the occurrence must 18 belong to the same specie; iii) The surrounding specie must be representative in the street (>50%); 19 iv) Visual analysis of street/avenue medians. Microscale analysis through supervised classification 20 and micrometeorological simulations od strong winds were performed. Morus nigra L., Tipuana tipu 21 (Benth.) Kuntze, Liriodendron tulipifera L., Prunus cerasifera Ehrh. and Koelreuteria paniculata Laxm. 22 were identified as the species that fall the most. In 57.7% of cases (425 fallen trees), the wind speed 23 12-hours before the occurrence was greater than 7 m s−1. Alvalade neighborhood showed 22.7% tree 24 canopy cover while the microclimatic simulation revealed two main vulnerability zones: Brazil and 25 Church avenues, where winds were stronger possibly due acceleration effect. 26

Regional thermal patterns in Portugal using satellite images (NOAA AVHRR)

In this paper two NOAA AVHRR diurnal images (channel 4) are used to determine the required procedures aiming at a future operational analysis system in Portugal. Preprocessing and classification operations are described. Strong correlation between air and surface temperature is verified and rather detailed air temperature patterns can be inferred.